1. Field of the Invention
This invention relates to microwave modules and, more specifically, to a method and material for use in conjunction with the lids of microwave modules to lower the Q of the cavities within the module to suppress electromagnetic resonance therein and reduce electromagnetic crosstalk between sections of the module, even for frequencies where there is an absence of resonance.
2. Brief Description of the Prior Art
In microwave circuitry, it is known that there can be electromagnetic resonance within the cavities of the microwave module containing the circuitry therein. This resonance causes undesirable EMI problems. It is also known that these EMI problems can be minimized by lowering the Q of the cavities within the module. The lowered Q suppresses the electromagnetic resonance and thereby minimizes the EMI problems. Even for frequencies where there is an absence of resonance, EMI crosstalk between different areas of the module can be reduced by the presence of microwave absorbing material.
In the prior art, EMI within the module has been reduced by producing a sheet of absorber material, such as, for example elastomer filled with iron powder, cutting out a pattern from the sheet of absorber material to fit around the components within the module, this pattern generally being very complex in shape, and then bonding the absorber to the module lid with an adhesive. The positioning of the absorber material on the lid has to be precise and of sufficient accuracy so that the pattern is positioned to fit around walls and components within the module without interference with components and module case features. This prior art procedure has provided the desirable result of EMI reduction, but only at great relative expense due to the precision shaping and positioning required of the sheet of absorber material.